In the consumer market, it would be desirable to have drills and power screwdrivers which have a variable speed transmission automatically changing the speed of the output spindle in response to torque. Variable two-speed drive is desirable so that during the insertion of a threaded fastener, the threaded fastener can rotate rapidly at the beginning of insertion into the part and towards the end of insertion, the transmission gears down moving it to a slower speed applying more torque onto the threaded fastener to shore-up the fastener upon full insertion of the fastener into the part. The variable transmission prevents motor burnout in the high speed mode as well as enabling the motor to work more efficiently. Of course, these designs are not unique to consumer devices, but are equally desirable for professional power tools.